Metal-oxide-semiconductor (MOS) transistors are one of the most important components in modern integrated circuits. A basic structure of the MOS transistor includes a semiconductor substrate, a gate structure on a surface of the semiconductor substrate, and source and drain doped regions in the semiconductor substrate on both sides of the gate structure. The gate structure includes a gate dielectric layer on the surface of the semiconductor substrate and a gate electrode layer on a surface of the gate dielectric layer.
With the development of semiconductor technologies, the control capability of the conventional planar MOS transistor over a channel current becomes weaker, causing a serious leakage current. A fin field effect transistor (FinFET) is one of emerging multifaceted-gate devices. The FinFET generally includes one or more protruding fins on a surface of a semiconductor substrate, a gate structure across a length portion of the fin and covering a portion of each of top and sidewall surfaces of the fin, and source and drain doped regions in the fin on both sides of the gate structure.
However, the performance of the semiconductor device conventionally formed by the FinFET still needs to be improved. The disclosed methods and device structures are directed to solve one or more problems set forth above and other problems.